According to the state of the art, fiber panels and/or wood chip panels are fabricated from a great variety of material compositions, which include panels made of wood chips or fibers held together by a binder, commonly known in the trade as oriented strand board (OSB) and medium density fiber board (MDF) panels. Such products may be in configurations designated as sheets, boards, panels, or the like, which are all generally termed "panels" throughout this specification.
In manufacturing such panels, the fibers or chips are mixed with the binder to form a moldable mass, which is then supplied to a former such as a sheet extruder. The former forms the moldable mass into an intermediate product such as an extruded sheet or band, which is then pressed in a heated press apparatus. During a predetermined pressing time, using a relatively high temperature, the pre-formed material composition is continuously or discontinuously hot-pressed into the form of panels or an endless band-shaped web. Thereafter, the material is either directly unloaded or first conveyed to a saw, the edges of the panels are squared and trimmed, and then the panels are conveyed, for example by a roller table, to a set of star wheels or turning devices. From the turning devices, the panels are conveyed over a second roller table to a stacker, and finally the panels are stored in an intermediate storage facility.
Directly after the hot-pressing of the panels, the outer surface of each panel has a temperature of more than 100.degree. C., and especially at least 110.degree. C., or even more than 120.degree. C. Thus, it is necessary to cool the material after the hot-pressing operation, in view of handling and quality requirements. The cooling of the panels already begins while the edges of the panels are being squared and trimmed. The cooling of the panels continues while the panels are being conveyed to the so-called star wheels or turning devices. Thus, depending on the respective thickness of each panel, the panels leave the cooling process with a panel temperature of about 60 to 80.degree. C. The cooling medium is conventionally air, which removes heat from the panel surfaces in a purposeful and targeted manner or a passive manner.
The conventional cooling process requires a relatively long time duration, depending on the thickness of the respective panel. Typically, after leaving the equipment at a temperature between 60.degree. C. and 80.degree. C. (intermediate panel temperature), the panels cool further to a normal room temperature by themselves, i.e. without any further active cooling efforts, while the panels are intermediately stored. This final cooling can take several days before the panels are cooled to normal room temperature. Such a long cooling time requires a corresponding large storage capacity for the intermediate storage of the panels. Namely, since it takes several days for the panels to completely cool down, the storage capacity of a panel manufacturing plant must be sufficient to store several days worth of the total output capacity of the plant. For cost reasons, such a large storage capacity should be avoided. Moreover, the structural length of the panel manufacturing equipment must also be rather long to provide sufficient time for the initial cooling of the panels, such that the length of the plant from the hot press to the last star wheel can amount to 80 meters, which is a further disadvantageous cost factor.
Another factor that must be considered is the desire to reduce the extent to which the panel manufacturing process impacts the environment. In this regard, it is a serious disadvantage of the conventional processes, that a considerable quantity of volatile binder vapors, such as formaldehyde and urea vapors, as well as dust and the like are released into the atmosphere during the rather long time period required for reducing the temperature of the panel surfaces to approximately 100.degree. C. Efforts to recover and reprocess the environmentally damaging binder vapors, dust and other harmful materials is quite costly, cumbersome, and not adequately effective.
Moreover, further disadvantages have resulted in practice due to the non-uniform removal of heat from the panels, leading to a non-uniform panel surface temperature in the cooling path from the panel press to the star wheels and in the star wheels themselves. This non-uniform panel temperature disadvantageously leads to warping of the panels, which requires a considerable post-processing effort, for example grinding, sanding, re-pressing or re-laminating in order to produce an acceptable marketable product.
In summary of the above, the known or conventional methods as described above suffer the following disadvantages:
a) the cooling time required for adequately cooling the panels is too long; PA1 b) the process results in a considerable impact on the environment through the process exhaust gases, which include after-vaporized binder components as well as process dust; and PA1 c) it is not possible to achieve a uniform removal of the surface heat from the panels.